1. Field of the Invention
The subject invention relates to a light emitting assembly of the type including light emitting diodes (L.E.D.s), and more particularly, to the avoidance of high temperatures causing early degradation of the L.E.D.s.
2. Description of the Prior Art
Light assemblies including light emitting diodes are often preferred over other light assembles due to their high efficiency. At least a fifty percent (50%) energy savings is possible when light assemblies including high intensity discharge (H.I.D.) lights are replaced with properly designed L.E.D. light assemblies. An example of such an L.E.D. light assembly is disclosed in U.S. Pat. No. 5,857,767 to the present inventor, Peter A. Hochstein, which is directed to effective thermal management. The '767 patent discloses a light assembly including a plurality of light emitting diodes disposed on a mounting surface of a heat sink. The heat sink includes a plurality of fins to increase the surface area of the heat sink and thus the amount of heat transferred from the light emitting diodes to surrounding ambient air. The expected life of such L.E.D. light assemblies can exceed 10-12 years, compared to a nominal 2-3 year life of H.I.D. light assemblies. When municipalities and other entities retrofit standard H.I.D. light assemblies with L.E.D. light assemblies, the L.E.D. light assemblies typically pay for themselves through energy related cost savings in 4-5 years.
However, as the power densities of L.E.D. assemblies continues to rise, the need for more effective thermal management increases. The cost-benefit calculus of L.E.D. light assemblies is marginal unless the useful life of the L.E.D.s is at least seven years. Unfortunately, thermal management of existing L.E.D. light assemblies may be inadequate at higher power densities due to the orientation of the heat sink, housing, or support of the light assembly. The inadequate or limited thermal management causes the L.E.D. light assemblies to operate at high junction temperatures, which leads to early degradation of the L.E.D.s.